A bending process for a corrugated product is known in the art, for example, as disclosed in the following patent publications:
Patent Publication No. 1: JP Patent Publication No. 2008-087033;
Patent Publication No. 2: JP Patent Publication No. 2006-136896;
Patent Publication No. 3: JP Patent Publication No. 2003-115567;
Patent Publication No. 4: JP Patent Publication No. 2006-015388;
Patent Publication No. 5: JP Patent Publication No. H11-179438;
Patent Publication No. 6: JP Patent Publication No. H09-155460.
According to one of conventional machines for the bending process, for example, as shown in FIG. 7 attached to the present application, multiple fixed dies 1, each of which has a recess Cm at a forward end for carrying out a press work so as to form a material M in a corrugated shape, are arranged in a line neighboring to each other. In a similar manner, multiple movable dies (press punches) 2, each of which has a punching forward end and is operatively punched into the respective recesses Cm, are arranged in a line neighboring to each other. According to the above processing machine, the multiple press punches 2 are simultaneously pushed down to the material M inserted into a working space between the fixed dies 1 and the movable dies 2, so as to carry out the press work and to form the material M in a corrugated shapes.
According to another prior art method for forming multiple corrugated portions by one press work, for example, as disclosed in the Patent Publication No. 1 (JP 2008-087033), a corrugated portion formed in a strip metal plate is held by a temporal holding portion, and then further corrugated portions (two corrugated portions) are sequentially formed by one press work in the strip metal plate in a direction from the temporarily held corrugated portion toward a material feeding portion. As above, the multiple corrugated portions are sequentially formed one after another in one press work.
According to a further prior art, for example, as shown in FIG. 8 attached to the present application, a corrugated portion is formed in a strip metal plate one by one in order to avoid a breaking of material. According to the machine and method for the bending process, multiple fixed dies 1 each having a recess Cm are arranged in a line in which the fixed dies are neighboring to each other. Multiple punches 2 are sequentially moved down toward the fixed dies 1 one by one, while the material M is fed to a press work area between the fixed dies and punches, so as to carry out the press work. More in detail, a corrugated portion is formed in the material M at a first press work point, the press punch 2 is lifted up so that the material M is further fed until the corrugated portion processed at the first press work point is moved to a second press work point, and another press punch 2 neighboring to the first press work point is pushed down to the fixed die 1 so as to surely keep the corrugated shape. During the press work at the second press work point, a portion of the material M is further pulled into the second press work point (the recess Cm of the fixed die 1).
The corrugated shape of the material M is likely to restore to its original flat shape to some extent by its elasticity, when the material M is processed by the press work at the first press work point. According to the above method, the press work is further carried out to the corrugated portion at the second press work point, so that the corrugated shape of the material M is maintained.
In a case that a larger number of corrugated portions will be formed, it will be necessary to carry out the press work at a higher speed. A method for forming multiple corrugated portions is proposed in the art, according to which multiple corrugated portions are formed in one stroke with time differences between respective press works. For example, as shown in FIG. 9 or 10, multiple press punches 2 are arranged in a line and a movable cam 3 is moved in a direction along the line of the press punches 2. The movable cam 3 has a pressing surface at its forward end, wherein the pressing surface is inclined by 45 degrees with respect to the moving direction of the movable cam 3. Therefore, when the movable cam 3 is moved in the forward direction, each of the press punches 2 is sequentially pushed down in a predetermined stroke “d”, so that the press work is carried out to the material M to form the corrugated shape. The above explained method is disclosed, for example, in the Patent Publication No. 2 (JP 2006-436896).
A further method for forming multiple corrugated portions is known in the art, for example, as disclosed in the Patent Publication No. 3 (JP 2003-115567), according to which multiple first punches and multiple second punches are arranged in a comb-shaped condition so that the first and second punches are opposing to each other. According to the prior art, a corrugated fin having a rectangular cross section is manufacture.
According to the Patent Publication No. 4 (JP 2006-15388), each of two press punches is alternately moved up and down so as to continuously manufacture a concavo-convex fin having a rectangular cross section from a flat thin metal plate.
Furthermore, a method for alternately moving two press punches up and down is disclosed in the Patent Publication No. 6 (JP H09-155960).
According to the Patent Publication No. 5 (JP H11-179438), upper and lower press punches are alternately operated in a sequential manner having a time difference between alternate operations of the upper and lower press punches, so as to carry out press works to a strip metal plate.
According to the conventional method, for example, as disclosed in the Patent Publication No. 1, the multiple corrugated portions can be formed by one press work in order to increase a working efficiency. However, it may have a problem that the breaking of the material or a shape distortion (such as a bowing of a product as shown in FIG. 11 attached to the present application) may occur.
According to the other convention method, for example, as disclosed in the Patent Publication No. 2, it is possible to continuously form the multiple corrugated portions by the movement of the movable cam. The movable cam 3 has the pressing surface at its forward end, wherein the pressing surface is inclined by 45 degrees with respect to the moving direction of the movable cam 3. Each of the press punches 2 are moved down by the predetermined stroke “d”, when the movable cam 3 is operated in the forward direction. However, an aspect ratio of the stoke “d” with respect to a width “P” of the press punch 2 is generally smaller than 1. In other words, a direction of movement of the cam 3 is in parallel to the line in which the multiple press punches are arranged, that is, the width direction of the press punches. Therefore, even when the pressing surface of the movable cam 3 having the 45-degree inclined surface is moved by the width “P”, the stroke “d” of the press punch 2 is smaller than “P” (P>d). As a result, in case of the material having a large aspect ratio or a high Young's modulus, the shape distortion may occur.
According to the Patent Publications Nos. 3 to 6, the upper dies and lower dies are moved up and down with the time differences. However, nothing is disclosed in the above prior art about the material having the large aspect ratio or the high Young's modulus.
A further proposal is made as shown in FIG. 12 attached to the present application, according to which a movable cam 3 is so arranged that the movable cam 3 is movable relative to a press punch 2 along a longitudinal direction of the press punch 2. The movable cam 3 has an inclined surface portion at its forward end, wherein the inclined surface portion is inclined by 45 degrees with respect to the longitudinal direction of the press punch 2. According to such an arrangement, a stroke of the press punch 2 in the downward direction is increased.
According to the above structure, however, since only a one side of the press punch 2, that is, a rear side end of the press punch 2 is in contact with the movable cam 3 (so-called a one-side contacting condition), a forward end of the press punch 2 may be lifted up.